Chrysotile

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Chrysotile
Chrysotile 1.jpg
General
Category Phyllosilicates
Kaolinite-serpentine group
Formula
(repeating unit)		 Mg 3(Si 2 O 5)(OH)4
(ideal)
IMA symbol Ctl [1]
Strunz classification 9.ED.15
Crystal system Monoclinic: clinochrysotile (most common)
Orthorhombic: orthochrysotile and parachrysotile (both rare)
Crystal class Clinochrysotile: prismatic (2/m)
Orthochrysotile and parachrysotile: pyramidal (mm2)
Space group Clinochrysotile: C2/m
Orthochrysotile and parachrysotile: Ccm21
Identification
Formula mass 277.11 g/mol (ideal)
ColourWhite to greyish green
Crystal habit Acicular
Fracture Fibrous
Mohs scale hardness2.5–3
Lustre Silky
Streak White
Diaphaneity Translucent
Density 2.53 g/ml
Optical propertiesBiaxial (+)
Refractive index nα = 1.569, nγ = 1.570
Birefringence 0.001 (max)
Dispersion Relatively weak
Extinctionparallel
Melting point 600–850 °C (1,112–1,562 °F) (decomposes)
Fusibility dehydrates at 550–750 °C (1,022–1,382 °F)
Diagnostic featuresWhite to grayish green thin, flexible curved fiber
Solubility Insoluble in water
Fibres degrade in dilute acid
References [2] [3] [4]

Chrysotile or white asbestos is the most commonly encountered form of asbestos, [5] accounting for approximately 95% of the asbestos in the United States [6] and a similar proportion in other countries. [7] It is a soft, fibrous silicate mineral in the serpentine subgroup of phyllosilicates; as such, it is distinct from other asbestiform minerals in the amphibole group. Its idealized chemical formula is Mg 3(Si 2 O 5)(OH)4. [5] The material has physical properties which make it desirable for inclusion in building materials, but poses serious health risks when dispersed into air and inhaled.

Contents

Polytypes

Three polytypes of chrysotile are known. [8] These are very difficult to distinguish in hand specimens, and polarized light microscopy [6] must normally be used. Some older publications refer to chrysotile as a group of minerals—the three polytypes listed below, and sometimes pecoraite as well—but the 2006 recommendations of the International Mineralogical Association prefer to treat it as a single mineral with a certain variation in its naturally occurring forms. [9]

Name Crystal system Type locality mindat.org reference Unit cell parametersCrystal structure reference
Clinochrysotile monoclinic Złoty Stok*, Lower Silesia, Poland 1071 a = 5.3 Å; b = 9.19 Å; c = 14.63 Å; β = 93° [10]
Orthochrysotile orthorhombic Kadapa* district, Andhra Pradesh, India 3025 a = 5.34 Å; b = 9.24 Å; c = 14.2 Å [11]
Parachrysotile orthorhombic uncertain 3083 a = 5.3 Å; b = 9.24 Å; c = 14.71 Å [12]
Source: mindat.org.
*Złoty Stok and Kadapa have formerly been known as Reichenstein and Cuddapah respectively, and these names may appear in some publications.

Clinochrysotile is the most common of the three forms, found notably at Val-des-Sources, Quebec, Canada. Its two measurable refractive indices tend to be lower than those of the other two forms. [13] The orthorhombic paratypes may be distinguished by the fact that, for orthochrysotile, the higher of the two observable refractive indices is measured parallel to the long axis of the fibres (as for clinochrysotile); whereas for parachrysotile the higher refractive index is measured perpendicular to the long axis of the fibres.[ citation needed ]

Physical properties

SEM photo of chrysotile Chrysotile SEM photo.jpg
SEM photo of chrysotile

Bulk chrysotile has a hardness similar to a human fingernail and is easily crumbled to fibrous strands composed of smaller bundles of fibrils. Naturally-occurring fibre bundles range in length from several millimetres to more than ten centimetres, [5] although industrially-processed chrysotile usually has shorter fibre bundles. The diameter of the fibre bundles is 0.1–1  μm, and the individual fibrils are even finer, 0.02–0.03 μm, each fibre bundle containing tens or hundreds of fibrils. [7]

Chrysotile fibres have considerable tensile strength, and may be spun into thread and woven into cloth. They are also resistant to heat and are excellent thermal, electrical and acoustic insulators. [5] [7]

Chemical properties

The idealized chemical formula of chrysotile is Mg 3(Si 2 O 5)(OH)4, although some of the magnesium ions may be replaced by iron or other cations. Substitution of the hydroxide ions for fluoride, oxide or chloride is also known, but rarer. [5] A related, but much rarer, mineral is pecoraite, in which all the magnesium cations of chrysotile are substituted by nickel cations.[ citation needed ]

Chrysotile is resistant to even strong bases (asbestos is thus stable in high pH pore water of Portland cement), but when the fibres are attacked by acids, the magnesium ions are selectively dissolved, leaving a silica skeleton. It is thermally stable up to around 550 °C (1,022 °F), at which temperature it starts to dehydrate. Dehydration is complete at about 750 °C (1,380 °F), with the final products being forsterite (magnesium silicate), silica and water. [7]

The global mass balance reaction of the chrysotile dehydration can be written as follows:

The chrysotile (serpentine) dehydration reaction corresponds to the reverse of the forsterite (Mg-olivine) hydrolysis in the presence of dissolved silica (silicic acid).

Applications

Previously, in the 1990s it was used in asbestos-cement products (like pipes and sheets). [14]

Magnesium sulfate (MgSO4) may be produced by treating chrysotile with sulfuric acid (H2SO4). [15]

Safety concerns

Chrysotile asbestos White asbestos (Chrysotile).jpg
Chrysotile asbestos

Chrysotile has been included with other forms of asbestos in being classified as a human carcinogen by the International Agency for Research on Cancer (IARC) [16] and by the U.S. Department of Health and Human Services. [5] These state that "Asbestos exposure is associated with parenchymal asbestosis, asbestos-related pleural abnormalities, peritoneal mesothelioma, and lung cancer, and it may be associated with cancer at some extra-thoracic sites". [17] In other scientific publications, epidemiologists have published peer-reviewed scientific papers establishing that chrysotile is the main cause of pleural mesothelioma. [18] [19] [20]

Chrysotile has been recommended for inclusion in the Rotterdam Convention on Prior Informed Consent, [21] an international treaty that restricts the global trade in hazardous materials. If listed, exports of chrysotile would only be permitted to countries that explicitly consent to imports. Canada, a major producer of the mineral, has been harshly criticized by the Canadian Medical Association [22] [23] for its opposition to including chrysotile in the convention. [24]

According to EU Regulation 1907/2006 (REACH) the marketing and use of chrysotile, and of products containing chrysotile, are prohibited. [25]

As of March 2024, the U.S. Environmental Protection Agency finalized regulations banning imports of chrysotile asbestos (effective immediately) due to its link to lung cancer and mesothelioma. However, the new rules can allow up to a dozen years to phase out the use of chrysotile asbestos in some manufacturing facilities. [26] The long phase-out period was a result of a strong lobby by Olin Corporation, a major chemical manufacturer, as well as trade groups like the U.S. Chamber of Commerce and the American Chemistry Council. Chrysotile asbestos is now banned in more than 50 other countries.

Critics of safety regulations

1990s: Canada-European dispute GATT dispute

In May 1998, Canada requested consultations before the WTO and the European Commission concerning France's 1996 prohibition of the importation and sale of all forms of asbestos. Canada said that the French measures contravened provisions of the Agreements on Sanitary and Phytosanitary Measures and on Technical Barriers to Trade, and the GATT 1994. The EC claimed that safer substitute materials existed to take the place of asbestos. It stressed that the French measures were not discriminatory under the terms of international trade treaties, and were fully justified for public health reasons. The EC further claimed that in the July consultations, it had tried to convince Canada that the measures were justified, and that just as Canada broke off consultations, it (the EC) was in the process of submitting substantial scientific data in favour of the asbestos ban. [27]

2000s: Canadian exports face mounting global criticism

In the late 1990s and early 2000s, the Government of Canada continued to claim that chrysotile was much less dangerous than other types of asbestos. [28] Chrysotile continued to be used in new construction across Canada, in ways that are very similar to those for which chrysotile was exported. [29] Similarly, Natural Resources Canada once stated that chrysotile, one of the fibres that make up asbestos, was not as dangerous as once thought. According to a fact sheet from 2003, "current knowledge and modern technology can successfully control the potential for health and environmental harm posed by chrysotile". [30] The Chrysotile Institute, an association partially funded by the Canadian government, also prominently asserted that the use of chrysotile did not pose an environmental problem and the inherent risks in its use were limited to the workplace. [31]

However, under increasing criticism by environmental groups, in May, 2012, the Canadian government stopped funding the Chrysotile Institute. [32] [33] As a result, the Chrysotile Institute has now closed. [34] [35] [36]

The Canadian government continues to draw both domestic and international criticism for its stance on chrysotile, most recently in international meetings about the Rotterdam Convention hearings regarding chrysotile. The CFMEU pointed out that most exports go to developing countries. Canada has pressured countries, including Chile, and other UN member states to avoid chrysotile bans. [37]

In September 2012, governments in Quebec and Canada ended official support for Canada's last asbestos mine in Asbestos, Quebec, [38] now renamed as Val-des-Sources.

See also

Related Research Articles

<span class="mw-page-title-main">Talc</span> Hydrated magnesium phyllosilicate mineral

Talc, or talcum, is a clay mineral composed of hydrated magnesium silicate, with the chemical formula Mg3Si4O10(OH)2. Talc in powdered form, often combined with corn starch, is used as baby powder. This mineral is used as a thickening agent and lubricant. It is an ingredient in ceramics, paints, and roofing material. It is a main ingredient in many cosmetics. It occurs as foliated to fibrous masses, and in an exceptionally rare crystal form. It has a perfect basal cleavage and an uneven flat fracture, and it is foliated with a two-dimensional platy form.

<span class="mw-page-title-main">Amphibole</span> Group of inosilicate minerals

Amphibole is a group of inosilicate minerals, forming prism or needlelike crystals, composed of double chain SiO
4 tetrahedra, linked at the vertices and generally containing ions of iron and/or magnesium in their structures. Its IMA symbol is Amp. Amphiboles can be green, black, colorless, white, yellow, blue, or brown. The International Mineralogical Association currently classifies amphiboles as a mineral supergroup, within which are two groups and several subgroups.

<span class="mw-page-title-main">Actinolite</span> Mineral

Actinolite is an amphibole silicate mineral with the chemical formula Ca2(Mg4.5–2.5Fe2+0.5–2.5)Si8O22(OH)2.

<span class="mw-page-title-main">Tiger's eye</span> Chatoyant gemstone from the quartz family

Tiger's eye is a chatoyant gemstone that is usually a metamorphic rock with a golden to red-brown colour and a silky lustre. As members of the quartz group, tiger's eye and the related blue-coloured mineral hawk's eye gain their silky, lustrous appearance from the parallel intergrowth of quartz crystals and altered amphibole fibres that have mostly turned into limonite.

<span class="mw-page-title-main">Mesothelioma</span> Cancer associated with asbestos

Mesothelioma is a type of cancer that develops from the thin layer of tissue that covers many of the internal organs. The area most commonly affected is the lining of the lungs and chest wall. Less commonly the lining of the abdomen and rarely the sac surrounding the heart, or the sac surrounding the testis may be affected. Signs and symptoms of mesothelioma may include shortness of breath due to fluid around the lung, a swollen abdomen, chest wall pain, cough, feeling tired, and weight loss. These symptoms typically come on slowly.

<span class="mw-page-title-main">Serpentine subgroup</span> Group of phyllosilicate minerals

Serpentine subgroup are greenish, brownish, or spotted minerals commonly found in serpentinite. They are used as a source of magnesium and asbestos, and as decorative stone. The name comes from the greenish color and smooth or scaly appearance from the Latin serpentinus, meaning "snake-like".

<span class="mw-page-title-main">Tremolite</span> Amphibole, double chain inosilicate mineral

Tremolite is a member of the amphibole group of silicate minerals with composition Ca2(Mg5.0-4.5Fe2+0.0-0.5)Si8O22(OH)2. Tremolite forms by metamorphism of sediments rich in dolomite and quartz, and occurs in two distinct forms, crystals and fibers. Tremolite forms a series with actinolite and ferro-actinolite. Pure magnesium tremolite is creamy white, but the color grades to dark green with increasing iron content. It has a hardness on Mohs scale of 5 to 6. Nephrite, one of the two minerals known as the gemstone jade, is a green crystalline variety of tremolite.

<span class="mw-page-title-main">Diopside</span> Pyroxene mineral

Diopside is a monoclinic pyroxene mineral with composition MgCaSi
2O
6. It forms complete solid solution series with hedenbergite and augite, and partial solid solutions with orthopyroxene and pigeonite. It forms variably colored, but typically dull green crystals in the monoclinic prismatic class. It has two distinct prismatic cleavages at 87 and 93° typical of the pyroxene series. It has a Mohs hardness of six, a Vickers hardness of 7.7 GPa at a load of 0.98 N, and a specific gravity of 3.25 to 3.55. It is transparent to translucent with indices of refraction of nα=1.663–1.699, nβ=1.671–1.705, and nγ=1.693–1.728. The optic angle is 58° to 63°.

<span class="mw-page-title-main">Riebeckite</span> Sodium-rich member of the amphibole group of silicate minerals

Riebeckite is a sodium-rich member of the amphibole group of silicate minerals, chemical formula Na2(Fe2+3Fe3+2)Si8O22(OH)2. It forms a solid solution series with magnesioriebeckite. It crystallizes in the monoclinic system, usually as long prismatic crystals showing a diamond-shaped cross section, but also in fibrous, bladed, acicular, columnar, and radiating forms. Its Mohs hardness is 5.0–6.0, and its specific gravity is 3.0–3.4. Cleavage is perfect, two directions in the shape of a diamond; fracture is uneven, splintery. It is often translucent to nearly opaque.

<span class="mw-page-title-main">Cummingtonite</span> Silicate mineral

Cummingtonite is a metamorphic amphibole with the chemical composition (Mg,Fe2+
)
2(Mg,Fe2+
)
5Si
8O
22(OH)
2, magnesium iron silicate hydroxide.

<span class="mw-page-title-main">Serpentinization</span> Formation of serpentinite by hydration and metamorphic transformation of olivine

Serpentinization is a hydration and metamorphic transformation of ferromagnesian minerals, such as olivine and pyroxene, in mafic and ultramafic rock to produce serpentinite. Minerals formed by serpentinization include the serpentine group minerals, brucite, talc, Ni-Fe alloys, and magnetite. The mineral alteration is particularly important at the sea floor at tectonic plate boundaries.

<span class="mw-page-title-main">Serpentine soil</span> Soil type

Serpentine soil is an uncommon soil type produced by weathered ultramafic rock such as peridotite and its metamorphic derivatives such as serpentinite. More precisely, serpentine soil contains minerals of the serpentine subgroup, especially antigorite, lizardite, and chrysotile or white asbestos, all of which are commonly found in ultramafic rocks. The term "serpentine" is commonly used to refer to both the soil type and the mineral group which forms its parent materials.

Asbestiform is a crystal habit. It describes a mineral that grows in a fibrous aggregate of high tensile strength, flexible, long, and thin crystals that readily separate. The most common asbestiform mineral is chrysotile, commonly called "white asbestos", a magnesium phyllosilicate part of the serpentine group. Other asbestiform minerals include riebeckite, an amphibole whose fibrous form is known as crocidolite or "blue asbestos", and brown asbestos, a cummingtonite-grunerite solid solution series.

Occupational lung diseases comprise a broad group of diseases, including occupational asthma, industrial bronchitis, chronic obstructive pulmonary disease (COPD), bronchiolitis obliterans, inhalation injury, interstitial lung diseases, infections, lung cancer and mesothelioma. These can be caused directly or due to immunological response to an exposure to a variety of dusts, chemicals, proteins or organisms. Occupational cases of interstitial lung disease may be misdiagnosed as COPD, idiopathic pulmonary fibrosis, or a myriad of other diseases; leading to a delay in identification of the causative agent.

<span class="mw-page-title-main">Asbestos</span> Carcinogenic fibrous silicate mineral

Asbestos is a naturally occurring fibrous silicate mineral. There are six types, all of which are composed of long and thin fibrous crystals, each fibre being composed of many microscopic "fibrils" that can be released into the atmosphere by abrasion and other processes. Inhalation of asbestos fibres can lead to various dangerous lung conditions, including mesothelioma, asbestosis, and lung cancer. As a result of these health effects, asbestos is considered a serious health and safety hazard.

<span class="mw-page-title-main">Erionite</span> Fibrous mineral

Erionite is a naturally occurring fibrous mineral that belongs to a group of minerals called zeolites. It usually is found in volcanic ash that has been altered by weathering and ground water. Erionite forms brittle, wool-like fibrous masses in the hollows of rock formations and has an internal molecular structure similar to chabazite. Some properties of erionite are similar to the properties of asbestos; however, erionite is not currently regulated by the U.S. Environmental Protection Agency and there are no occupational exposure limits for erionite fibers. Erionite was first described by A.S. Eakle in 1898, as white woolly fibrous masses in cavities in rhyolite lava near Durkee, Oregon. It was originally thought to be another relatively rare zeolite named offretite, which is very similar to erionite in appearance and chemical composition.

<span class="mw-page-title-main">Balangeroite</span>

Balangeroite is found in one of the most important chrysotile mines in Europe, the Balangero Serpentinite. Hence, it is usually mistaken as an asbestiform in an assemblage of other mineral phases like chrysotile, magnetite and Fe-Ni alloys. However, Balangeroite does not lead to serious health problems caused by asbestos fibers.

<span class="mw-page-title-main">Asbestos Mountains</span> Range of hills in Northern Cape, South Africa

The Asbestos Mountains is a range of hills in the Northern Cape province of South Africa, stretching south-southwest from Kuruman, where the range is known as the Kuruman Hills, to Prieska. It passes Boetsap, Danielskuil, Lime Acres, Douglas and Griekwastad. The range lies about 150 kilometres (93 mi) west of Kimberley and rises from the Ghaap Plateau.

<span class="mw-page-title-main">Health impact of asbestos</span>

All types of asbestos fibers are known to cause serious health hazards in humans. The most common diseases associated with chronic exposure to asbestos are asbestosis and mesothelioma.

References

  1. ↑ Warr, L.N. (2021). "IMA–CNMNC approved mineral symbols". Mineralogical Magazine. 85 (3): 291–320. Bibcode:2021MinM...85..291W. doi: 10.1180/mgm.2021.43 . S2CID   235729616.
  2. ↑ Mineralienatlas
  3. ↑ Chrysotile on Mindat.org
  4. ↑ Chrysotile data on Webmineral
  5. 1 2 3 4 5 6 "Asbestos" (PDF). Report on Carcinogens, Eleventh Edition. U.S. Department of Health and Human Services. 2005.
  6. 1 2 Occupational Safety and Health Administration, U.S. Department of Labor (2007). 29 C.F.R. 1910.1001. Appendix J.
  7. 1 2 3 4 Institut national de recherche sur la sécurité (1997). "Amiante Archived 2008-06-25 at the Wayback Machine ." Fiches toxicologiques. n° 167. (in French)
  8. ↑ Wicks, F. J.; Whittaker, E. J. W. (1975). "A reappraisal of the structures of the serpentine minerals". The Canadian Mineralogist. 13 (3): 227–243.
  9. ↑ Burke, Ernst A. J. (2006). "A Mass Discreditation of GQN Minerals" (PDF). The Canadian Mineralogist. 44 (6): 1557–60. Bibcode:2006CaMin..44.1557B. doi:10.2113/gscanmin.44.6.1557. Archived from the original (PDF) on 2012-03-26. Retrieved 2010-11-30.
  10. ↑ Whittaker, E. J. W. (1956). "The structure of chrysotile. II. Clino-chrysotile". Acta Crystallographica. 9 (11): 855–62. Bibcode:1956AcCry...9..855W. doi: 10.1107/S0365110X5600245X .
  11. ↑ Whittaker, E. J. W. (1956). "The structure of chrysotile. III. Ortho-chrysotile". Acta Crystallographica. 9 (11): 862–64. Bibcode:1956AcCry...9..862W. doi: 10.1107/S0365110X56002461 .
  12. ↑ Whittaker, E. J. W. (1956). "The structure of chrysotile. IV. Para-chrysotile" (PDF). Acta Crystallographica. 9 (11): 865–67. Bibcode:1956AcCry...9..865W. doi:10.1107/S0365110X56002473.
  13. ↑ In principle, all polytypes of chrysotile should have three independent refractive indices: in practice, two of the three are so close as to be indistinguishable by experimental measurement.
  14. ↑ Pigg, B. J. (August 1994). "The uses of chrysotile". The Annals of Occupational Hygiene. 38 (4): 453–458, 408. doi:10.1093/annhyg/38.4.453. ISSN   0003-4878. PMID   7978966.
  15. ↑ Bedelova, Zh. D.; Tabylganova, A. N; Homyakov, A. P.; Dagubaeva, A. T. (2017). "DEVELOPING THE TECHNOLOGY OF WASTE SULFURIC ACID LEACHING OF CHRYSOTILE ASBESTOS PRODUCTION" (PDF). Machines. Technologies. Materials. 4. National center on complex processing of mineral raw materials of the Republic of Kazakhstan: 288–290. eISSN   1314-507X. ISSN   1313-0226.
  16. ↑ International Agency for Research on Cancer (1998). "Asbestos." However, the study states " In some of these case reports and in other studies, asbestos fibres have been identified in the lung. Amphibole fibres have usually predominated, but in a few cases mainly or only chrysotile fibres were found." IARC Monographs on Evaluating the Carcinogenic Risks to Humans. Supplement 7 Archived 2008-03-06 at the Wayback Machine .
  17. ↑ Agency for Toxic Substances and Disease Registry (ATDSR), U.S. Department of Health and Human Services (2007). "Asbestos Toxicity Archived June 6, 2011, at the Wayback Machine ." Case Studies in Environmental Medicine.
  18. ↑ "Archived copy" (PDF). Archived from the original (PDF) on 2010-06-09. Retrieved 2011-10-03.{{cite web}}: CS1 maint: archived copy as title (link) See e.g., Smith, Allen "Chrysotile is the main cause of pleural mesothelioma", Amer.J.Indus.Med., Vol. 32, pp. 252 to 266 (1996)
  19. ↑ Tossavainen A, "Asbestos, asbestosis, and cancer: the Helsinki criteria for diagnosis and attribution" Scand J Work Environ Health 1997;23(4):311–316 (stating that all types of malignant mesothelioma can be induced by asbestos, with the amphiboles showing greater carcinogenic potency than chrysotile)
  20. ↑ Lemen, Richard A. (2010). "Chrysotile Asbestos and Mesothelioma". Environmental Health Perspectives. 118 (7): a282. doi:10.1289/ehp.1002446. PMC   2920924 . PMID   20601327.
  21. ↑ Rotterdam Convention: Chrysotile
  22. ↑ Attaran, Amir; Boyd, David R.; Stanbrook, Matthew B. (October 2008). "Asbestos mortality: a Canadian export". CMAJ. 179 (9): 871–2. doi:10.1503/cmaj.081500. PMC   2565724 . PMID   18936444.
  23. ↑ Collier, Roger (December 2008). "Health advocates assail Canada's asbestos stance". CMAJ. 179 (12): 1257. doi:10.1503/cmaj.081806. PMC   2585122 . PMID   19047602.
  24. ↑ MITTELSTAEDT, MARTIN (September 10, 2008). "Canada still blocking action on asbestos". The Globe and Mail. Toronto. Retrieved 2008-10-01.
  25. ↑ Amtsblatt der Europäischen Union, L 396 from 30-12-2006 (PDF 1,8 MB; S. 129)
  26. ↑ U.S. Bans the Last Type of Asbestos Still in Use by Coral Davenport in the New York Times, Mar. 18, 2024.
  27. ↑ EC measures affecting asbestos products. World Trade Organization News. 29 October 1998
  28. ↑ Harper, Tim (3 July 2011). "Canada diminished by asbestos hypocrisy". The Chronicle Herald . Archived from the original on 20 November 2012. Retrieved 28 September 2012.
  29. ↑ Versailles, Guy (8 July 2015). "What Exactly Is Asbestos?". South Bay Mitigation.
  30. ↑ "Chrysolite Asbestos Fact Sheet" (PDF). Natural Resources Canada. 3 February 2009. Archived from the original (PDF) on 27 September 2007. Retrieved 2010-01-12.
  31. ↑ Vongdouangchanh, Bea (5 July 2011). "NDP MP Martin's one-man battle to ban asbestos mining in Canada gains traction". The Hill Times.
  32. ↑ "Asbestos Advocacy Group Shuts Its Doors, Montreal Gazette". Archived from the original on 2012-07-10. Retrieved 2018-10-04.
  33. ↑ "Canadian Cancer Society Disappointed with Proposed Federal Government Funding for Chrysotile Institute, 3 March 2012". Archived from the original on 28 June 2011. Retrieved 28 September 2012.
  34. ↑ R.I.P. Chrysotile Institute, The Mad Scientist Blog>
  35. ↑ Asbestos Advocacy Group Shuts Its Doors, Vancouver Sun, 29 April 2012 [ permanent dead link ]
  36. ↑ ""Minister Flaherty: Stop Funding The Chrysotile Institute", 2 Feb. 2011". Archived from the original on 2019-04-04. Retrieved 2012-09-28.
  37. ↑ Stop Canada's Export Of Asbestos CFMEU Archived July 10, 2010, at the Wayback Machine
  38. ↑ Daniel Lak (17 Oct 2012). "Canada axes support for asbestos mining". Al Jazeera.
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